Submergible pumping system with thermal sprayed polymeric wear surfaces

ABSTRACT

In a pumping system, a PEEK composite material may be applied to wear areas on internal components. Typically, the internal component provides a metallic substrate which is prepared with a metallic bonding layer arc sprayed onto its surface, at least at the wear area. A powderized PEEK composite material is heated and propelled against the substrate and bonding layer by a high velocity oxy fuel technique. This uniformly coats the substrate providing a durable wear surface for prolonging component life.

This application is a continuation of 09/159,132 filed Sep. 23, 1998 nowU.S. Pat. No. 6,012,900.

FIELD OF THE INVENTION

The present invention relates generally to polymeric coated wearsurfaces, and particularly to wear surfaces in a submergible pumpingsystem in which a polymeric material, such as a PEEK composite material,is bonded to the wear surface.

BACKGROUND OF THE INVENTION

Pumping systems, such as submergible and horizontal pumping systems, areutilized in pumping oil and/or other production fluids from producingwells. A typical submergible pumping system, for example, includescomponents, such as a motor, motor protector and a centrifugal pump.Each of these components has moving parts that are subject to wear. Thisis particularly true in the relatively harsh downhole environment inwhich many submergible pumping systems are used.

A variety of surfaces, such as thrust bearing surfaces in the motorprotector and/or centrifugal pump are subject to substantial wear.Similarly, other surfaces in the centrifugal pump, such as the impellerand diffuser vanes, the backwash area on the diffuser, impeller skirt,impeller balance ring, the diffuser wall, the diffuser bore and the hubsof the impellers are susceptible to wear. This is particularly true dueto grit, such as sand, that often is found suspended in the productionfluid.

Attempts have been made to provide a coating on the components at someof these wear areas. For example, thrust bearings have been produced inwhich the thrust bearing pads have a layer of PEEK material molded overthe bearing surface of the pad. However, this molding process isrelatively expensive and not conducive to coating many surface areas,such as the surfaces along the inside of a radius or diameter and othersurfaces with complex shapes.

Also, centrifugal pumps have incorporated wear rings on the impellerskirt and balance ring. Typically these rings are made of a more wearresistant material, however they can be fabricated of the same materialas the stage. Most recently, carbon fiber reinforced PEEK rings havebeen fabricated for use as wear rings. These wear rings range inthickness and size depending on the centrifugal pump, however the wearrings must be of sufficient cross sectional area to withstand thephysical stresses which tend to separate the wear ring from theimpeller. Such wear rings typically are held in place by an interferencefit which places the ring in tension. Sometimes, wear rings are retainedwith an adhesive bond or welding.

Having a process by which a polymeric material, specifically a PEEKcomposite material, could be applied to a wide variety of wear surfacesin a pumping system would be advantageous in reducing component wear.For example, it would be advantageous to allow for direct application ofa bonded wear surface of PEEK to replace the common practice of mating amachined wear ring of PEEK with a machined impeller. By directapplication of the PEEK wear surface, there is a greater flexibility inselecting the thickness and size of the wear surface.

SUMMARY OF THE INVENTION

The present invention features a method for protecting wear areas oninternal components used in a production fluid pumping system. Themethod comprises. providing a PEEK composite material in powderizedform. The PEEK composite material is then applied to the internalcomponent by heating the PEEK composite material and propelling itagainst the internal component.

According to another aspect of the invention, a fluid pumping system isprovided. The pumping system includes a plurality of wear areas, eachhaving a metal substrate coated by a bonding layer. A surface wear layeris deposited onto the bonding layer via a multiplicity of moltenplatelets that form the surface wear layer upon solidification. Thesurface wear layer comprises a PEEK composite material.

According to another aspect of the invention, a centrifugal pumputilizes at least one diffuser and at least one impeller to create afluid flow. A plurality of PEEK composite areas are disposed on matingsurfaces of the diffuser and impeller to reduce wear due to fluiderosion, sliding surface friction and/or three body wear at thatparticular area. Each PEEK composite area comprises a layer of PEEKcomposite bonded to at least one of the diffuser or the impeller.

According to a further aspect of the invention, a thrust bearing isprovided for use in a component of a pumping system. The thrust bearingincludes at least one thrust pad comprising a substrate pad, typicallymade of a metal material. A PEEK composite layer is formed on thesubstrate pad by a multiplicity of PEEK composite particles forcedtogether under high velocity at a temperature at least as high as themelting point of the PEEK composite material.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will hereafter be described with reference to theaccompanying drawings, wherein like reference numerals denote likeelements, and:

FIG. 1 is a front elevational view of an exemplary pumping systemdisposed within a wellbore;

FIG. 2 is a partial cross-sectional view taken generally along the axisof the motor protector of FIG. 1;

FIG. 3 is a top view of a thrust bearing, according to a preferredembodiment of the present invention;

FIG. 4 is a cross sectional view taken generally along line 4—4 of FIG.3;

FIG. 5 is an enlarged cross-sectional view taken generally at the region5—5 of FIG. 4;

FIG. 6 is a partial cross-sectional view taken generally along line 6—6at the submergible pump illustrated in FIG. 1;

FIG. 7 is an enlarged cross-sectional view taken generally at region 7—7of FIG. 6; and

FIG. 8 is an enlarged cross-sectional view of the region 8—8 of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring generally to FIG. 1, an exemplary pumping system 10, such as asubmergible pumping system, is illustrated. Pumping system 10 maycomprise a variety of components depending on the particular applicationor environment in which it is used. Typically, system 10 includes atleast a centrifugal pump 12, a motor 14 and a motor protector 16.

In the illustrated example, pumping system 10 is designed for deploymentin a well 18 within a geological formation 20 containing desirableproduction fluids, such as petroleum. In a typical application, awellbore 22 is drilled and lined with a wellbore casing 24. Wellborecasing 24 may include a plurality of openings 26 through whichproduction fluids may flow into wellbore 22.

Pumping system 10 is deployed in wellbore 22 by a deployment system 28that may have a variety of forms and configurations. For example,deployment system may comprise tubing 30 connected to pump 12 by aconnector 32. Power is provided to submergible motor 14 via a powercable 34. Motor 14, in turn, powers centrifugal pump 12 which drawsproduction fluid in through a pump intake 36 and pumps the productionfluid to the surface via tubing 30.

It should be noted that the illustrated submergible pumping system 10 ismerely an exemplary embodiment. Other components can be added to thesystem, and other deployment systems may be implemented. Additionally,the production fluids may be pumped to the surface through tubing 30 orthrough the annulus formed between deployment system 28 and wellborecasing 24. In any of these configurations of submergible pumping system10, it is desirable to attain the benefits of protected wear surfaces inaccordance with the present invention.

Referring to FIGS. 2-8, preferred embodiments of the present inventionare described. These embodiments are examples of how polymer coatings,such as PEEK composite coatings, can be utilized on a variety ofcomponents, that are subject to wear, in pumping systems. For example, aPEEK composite coating, according to the present invention, can beutilized on thrust bearings used in motor protector .16 and on impellerand diffuser surfaces within centrifugal pump 12.

Referring generally to FIG. 2, motor protector 16 is illustrated with aportion of its outer housing 38 broken away to expose a thrust bearingassembly 40 disposed therein. Thrust bearing assembly 40 may include,for example, an upper lock ring 42, an upper thrust bearing 44, and aring 46 disposed about central shaft 48. A high load thrust bearing 50is separated from lock ring 42 by a thrust bearing spacer 52.

The arrangement of the motor protector components are generally known tothose of ordinary skill in the art, and a variety of otherconfigurations may be employed. In any event, the high load thrustbearing 50 must be designed to support relatively high loads as theinternal components are rotated by shaft 48 against thrust bearing 50.Thus, the upper supporting surface of thrust bearing 50 is a primecandidate for wear. A coating of PEEK composite material, according to apreferred embodiment of the present invention, has a low coefficient offriction and excellent wear properties for use on such a wear surface.

An exemplary high load thrust bearing 50 is illustrated in FIGS. 3-5. Asillustrated, thrust bearing 50 includes a carrier ring 54 having acentral aperture 56 through which shaft 48 extends. Carrier ring 54includes a recessed area 58 for receiving a plurality of thrust pads 60.Thrust pads 60 are held in recessed area 58 by a retaining ring 62.Furthermore, carrier ring 54 includes a slot 64 for receiving ananti-rotation pin 66 to prevent rotational movement of thrust bearing50. Carrier ring 54 also includes a plurality of oil circulation holes68 disposed therethrough. A top surface 70 of each thrust pad 60 acts asthe loading area. Accordingly, top surface 70 of each thrust pad 60serves as a prime area for application of a PEEK composite coatingaccording to a preferred embodiment of the present invention.

As illustrated in FIG. 5, each pad 60 includes a substrate material orpad 72. Pad 72 is made of PH17-4stainless steel, however, other metalsand materials potentially may be used in the construction of anappropriate substrate.

As will be more fully described below, substrate 72 preferably isprepared by providing a roughened surface 74 to which a bonding layer 76is applied. A polymer layer, preferably a PEEK composite layer 78, isapplied to substrate 72 and bonding layer 76 via a high velocity oxyfuel (HVOF) process.

This HVOF process creates PEEK composite layer 78 by rapidlyaccelerating molten or partially molten particles of the PEEK compositematerial against bonding layer 76 and substrate 72. The stream of moltenor partially molten platelets that hit the bonding layer 76 form acontinuous coating, typically having a lamellar structure. The durablecoating has a low porosity, e.g. generally less than one percentporosity.

Another exemplary submergible pumping system component having aplurality of wear areas amenable to a durable coating of a PEEKcomposite, is centrifugal pump 12. Pump 12 is a centrifugal pump thatuses a plurality of impellers 80 and diffusers 82 to pump productionfluids. The impellers and diffusers have a plurality of wear areas thatbenefit from the application of a polymeric material, such as a PEEKcomposite material.

A portion of centrifugal pump 12 taken generally along line 6—6 of FIG.1, is illustrated in cross-section in FIG. 6. As illustrated, eachimpeller includes an impeller vane 84 that directs a production fluid tothe next sequential diffuser vane 86, as is understood by those ofordinary skill in the art. Each impeller 80 further includes an impellerhub 88 mounted to a central rotatable shaft 90. Thus, shaft 90 rotatesimpellers 80 within stationary diffusers 82. This configuration createscertain wear areas.

For example, each impeller includes an impeller skirt 92 that rotatesinside a stationary diffuser lip 94. There is a gap between these twosurfaces that allows fluid to flow between these surfaces. This fluidflow will cause erosion wear to occur on the mating surfaces 94 and 92due to the corrosive nature of the fluid, entrained grit, cavitation, ora combination of these wear mechanisms. Also, it is possible for slidingwear to occur between surface 94 and 92 due to tight clearances.

Additionally, each impeller includes a balance ring 96 that rotatesinside a corresponding support 98 of an adjacent diffuser 82, creatinganother wear area due to erosion, corrosion, erosion corrosion, threebody wear, and/or sliding wear. A further wear area exists between eachimpeller hub 88 and the surrounding inner wall 100 of the correspondingdiffuser 82. This area forms a journal bearing which radially supportsthe rotating impeller. 80 inside the stationary diffuser 82. Wear inthis area can be the result of sliding surfaces or wear due to fluidflow through the operating clearance.

Wear areas also can be created independent of the sliding movement andfluid leakage of each impeller 80 with respect to its correspondingdiffuser 82. For example, a wear area 102 may exist along an outerdiffuser wall 104 where the production fluids exit an impeller vane 84and impact against outer diffuser wall 104 as the production fluid isforced into the next sequential diffuser vane 86. This wear area alsobenefits from a durable, well-bonded coating of a polymeric material,specifically a PEEK composite material.

An exemplary wear area, which can be labeled wear area 106 is disposedbetween the impeller balance ring 96 and the stationary diffuser wall98. This wear area 106 is illustrated by the enlarged cross-section ofFIG. 7 taken generally along the line 7—7 of FIG. 6.

Wear area 106 is a prime exemplary area for applying a PEEK compositecoating. Potentially, a PEEK composite layer may be applied to both theinside diameter of diffuser wall 98 and the outside diameter of impellerbalance ring 96 or to one of the surfaces. In either case, the balancering 96 or the diffuser wall 98 comprises a metallic substrate 108 thatpreferably includes a roughened surface 110 to which a bonding layer 112is applied as illustrated in FIG. 8. A polymer layer, specifically aPEEK composite layer 114 is applied to bonding layer 112 and substrate108 as described above with reference to FIG. 5.

The preferred process for applying a PEEK composite material to wearareas within a submergible pumping system is described in detail below.This process permits application of a PEEK composite material to avariety of components and wear surfaces of myriad shapes. It isparticularly beneficial for the application of PEEK composite materialto inside radii and diameters, such as the inside diameter surface 116of diffuser wall 98 illustrated in FIG. 7.

The preferred process for creating and applying PEEK composite layer 78or 114 involves initial preparation of substrate layer 72, 96 or 98 forreceipt of a polymer layer via a thermal spray process. In the preferredembodiment, the substrate is a metallic material, such as Ni Resist orstainless steel but other metallic materials may be appropriatedepending on the specific application. A first step in the process ispreparation of the substrate material. The substrate material preferablyis cleaned by removing dirt, moisture, oil and other contaminants fromthe surface to be coated. To facilitate adherence, it is also desirableto roughen the surface to be coated. It is preferred that the surface beroughened by grit blasting. For example, the substrate may be gritblasted with aluminum oxide having a grit mesh size 28.

In another step of the process, the polymeric material is prepared foruse in coating the substrate, e.g. 72, 96 or 98. It is preferred thatthe polymeric material have a high melting temperature, i.e., above 300°C. In the most preferred embodiment, a PEEK material is used to preparea composite material in powdered form. Although a variety of materialsmay be mixed with the PEEK material, it has been determined that apreferred composite comprises a mixture of PEEK withpolytetrafluoroethylene (PTFE) and carbon. These materials enhance thelow coefficient of friction and excellent wear properties of PEEK.

An exemplary ratio of materials is approximately 70% PEEK mixed withapproximately 20% PTFE and approximately 10% carbon. Additionally, theselection of appropriate particle size can be critical to the HVOFprocess. It has been determined that optimal particle sizes for thevarious components of the PEEK composite are approximately 70 micronsfor the PEEK; approximately 53 microns for the PTFE; and approximately 6microns for the carbon particles. Although specific mixture percentagesand particle sizes have been provided, other mixture ratios, particlesizes, and mixture components may be amenable to the process of thepresent invention.

After cleaning and grit blasting of the substrate material, e.g. 72, 96or 98, a bonding layer, e.g. 76, 112, may be applied to the substrate.The bonding layer preferably is a metallic material having sufficientsurface asperities to facilitate the mechanical bonding of the PEEKcomposite layer to the substrate. Preferably, a single layer of metallicmaterial, such as nickel aluminum alloy, is applied. This material hasdesired characteristics at high temperature and provides excellentbonding to a stainless steel substrate. Other bonding layer materialsmay work better with substrates formed of materials other than stainlesssteel.

In the preferred embodiment, the nickel aluminum alloy is arc sprayedagainst the substrate. Arc spraying, as is generally known to those ofordinary skill in the art, uses a high energy electric arc generated bybringing two electrically energized wires into contact with each other.The arc energy melts the wires, and compressed air atomizes the moltenmaterial and propels it onto the substrate, leaving a bonding layer.Preferably, the bond layer has good thermal conductivity to helpdissipate heat from the PEEK layer, particularly when the PEEK materialis used as a bearing surface. It has been determined that an optimalthickness for the bond coat is in the range of approximately 0.014 to0.018 inches.

Following preparation of the substrate, application of the bondinglayer, and preparation of the PEEK composite material, the PEEKcomposite material is applied to the substrate over the bonding layer bya thermal spray. In the preferred embodiment, an HVOF process isutilized to apply the PEEK composite mixture to the substrate and thebonding layer. An optimum window of spray parameters has beenestablished to ensure low porosity and great bond strength to permit thePEEK composite layer to be used in load bearing environments as well asprotective coating environments.

Preferably, the HVOF process is carried out with the aid of a thermalspray gun, such as the Miller Thermal Spray Gun, Model HV2000, availablefrom Miller Thermal, Inc. The Thermal Spray Gun is equipped with anaxial powder feed configuration and is controlled by a Miller ThermalComputerized Console. The Thermal Spray Gun is equipped with a 12 mmcombustion chamber, and the fuel gas, preferably hydrogen, to oxygenratio is 3.33. Additionally, a carrier gas, preferably nitrogen, isflowed through the thermal spray gun at a flow rate of 30 scfh to feedpowder into the combustion chamber.

The powderized PEEK composite mixture is fed to the thermal spray gunvia an electronically controlled, pressurized hopper unit, as is wellknown to those of ordinary skill in the art. The PEEK composite materialis then injected through the flame of the HVOF thermal spray gun andheated to at least the melting point of the PEEK composite material,e.g. approximately 340° C. The powder particles of the PEEK compositeare partially or preferably fully melted and propelled towards thesubstrate and bonding layer. This creates a stream of semi-molten ormolten particles or platelets that hit the substrate to form acontinuous coating typically having a lamellar structure. A mechanicalinterlocking process takes place between the particles and the roughsubstrate/bonding layer to securely bond the continuous coating to thesubstrate.

In the preferred embodiment, the PEEK composite powder is fed at a rateof 11 grams per minute and the thermal spray gun is moved at a traversespeed of 754 millimeters per second with a standoff of 7 inches. (Thestandoff refers to the distance between the substrate and the outlet tipof the thermal spray gun.) The PEEK composite coating is built up inmultiple passes to a thickness between approximately 0.019 inches and0.021 inches. Typically, there is one preheat cycle and 30 passes,following which, the coating is allowed to cool by a natural slow cool.

After application of the PEEK composite mixture to form a PEEK compositelayer, e.g. PEEK composite layer 78 or 114, it may be advantageous toadopt a post-deposition annealing process. The post-deposition annealingprocess provides a more durable coating. It facilitates the removal ofthe thermal history and residual stress. It also increases the level ofcrystallinity of the PEEK composite coating.

A preferred post-deposition annealing process comprises heating the PEEKcomposite layer to approximately 400° C. and holding it at thattemperature for approximately 30 minutes. The PEEK composite layer (78,114), along with the substrate (72, 96 or 98) and bonding layer (76,112), then undergoes a controlled cooling to approximately 270° C. atwhich temperature it is held for approximately 10 minutes. Thereafter,the PEEK composite layer, substrate and bonding layer undergo acontrolled cooling to below 60° C.

The above-described method provides a PEEK composite coating that iseasily applied and has low porosity, typically on the order of less thanone percent porosity. The PEEK composite layer is particularly amenableto use as a bearing surface because of its low coefficient of friction,excellent wear properties and low porosity achieved with this process.

It will be understood that the foregoing description is of preferredexemplary embodiments of this invention, and that the invention is notlimited to the specific forms shown. For example, the method may beapplied to a wide variety of other components; the precise mixture ofconstituents in the PEEK composite may be adjusted for desiredapplications or effects; the HVOF parameters may be adjusted accordingto the PEEK composite mixture, the particulate size, the type of HVOFthermal spray gun utilized and the environment in which the process isimplemented; and the bonding layer material may be adjusted according tothe various other parameters, including the material used in formationof the substrate. These and other modifications may be made in thedesign and arrangement of the elements without departing from the scopeof the invention as expressed in the appended claims.

What is claimed is:
 1. A thrust bearing for use in a pumping system, thethrust bearing comprising: a carrier ring; a plurality of thrust padsmounted to the carrier ring; and a thermally sprayed PEEK compositelayer having a low porosity due to the uniform distribution of particlesof PEEK via thermal spraying, the thermally sprayed PEEK composite layerbeing located on the plurality of thrust pads and applied by an HVOFthermal spray.
 2. The thrust bearing as recited in claim 1, wherein eachthrust pad comprises a metal substrate.
 3. The thrust bearing as recitedin claim 2, further comprising a bond layer disposed between the metalsubstrate and the PEEK composite layer.
 4. The thrust bearing as recitedin claim 3, wherein the bond layer comprises a nickel aluminum alloy. 5.The thrust bearing as recited in claim 4, wherein the bond layer is arcsprayed to the metal substrate.
 6. The thrust bearing as recited inclaim 5, wherein the metal substrate comprises a steel material.
 7. Thethrust bearing as recited in claim 6, wherein the steel material iscast.
 8. A thrust bearing for use in a component of a pumping system,the thrust bearing including at least one thrust pad comprising: asubstrate pad; a multiplicity of PEEK composite particles; and athermally sprayed PEEK composite layer having a low porosity due to theuniform distribution of PEEK particles located on the substrate pad andapplied via a multiplicity of PEEK composite particles forced togetherunder high velocity at a temperature at least as high as the meltingpoint of the PEEK composite particles.
 9. The thrust bearing as recitedin claim 8, further comprising a metallic bond layer applied to thesubstrate to facilitate adherence of the PEEK composite layer to thesubstrate pad.
 10. The thrust bearing as recited in claim 9, wherein themetallic bond layer comprises an arc spray coating of a nickel aluminumalloy.
 11. The thrust bearing as recited in claim 9, wherein thesubstrate pad comprises a steel casting.
 12. The thrust bearing asrecited in claim 9, wherein the multiplicity of PEEK composite particlescomprises a mixture of PEEK particles, PTFE particles and carbonparticles.
 13. A system for applying PEEK to a thrust bearing for use ina pumping system, the system comprising: a carrier ring; a plurality ofthrust pads mounted to the carrier ring; and a means for applying amultiplicity of heated PEEK composite particles to the thrust pads suchthat the PEEK composite particles form a PEEK composite layer.
 14. Thesystem of claim 13, wherein each thrust pad comprises a metal substrate.15. The system of claim 14, further comprising a bond layer disposedbetween the metal substrate and the PEEK composite layer.
 16. The systemof claim 15, wherein the bond layer comprises a nickel alloy.
 17. Thesystem of claim 16, wherein the bond layer is arc sprayed to the metalsubstrate.
 18. The system of claim 17, wherein the metal substratecomprises a steel material.
 19. The system of claim 18, wherein thesteel material is cast.